
DETROIT PUBLIC SCHOOLS 



Department of Instruction, 
Teacher Training and Research 



STANDARDS and CONVENTIONS 
for MECHANICAL DRAWING 




Published by the Authority of the 

Board of Education 

City of Detroit 

1921 



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These Standards and Conventions for 
Mechanical Drawing were prepared by 
Frank R. Kepler, Supervisor of Me- 
chanical Drawing, Detroit Public 
Schools, revised by the Detroit Manual 
Training Club*s Standards Committee, 
and copyrighted in 1921 by him for the 
City of Detroit. 



DETROIT PUBLIC SCHOOLS 

Department of Instruction, 
Teacher Training and Research 



STANDARDS and CONVENTIONS 
for MECHANICAL DRAWING 




Published by the Authority of the 

Board of Education 

City of Detroit 

1921 






Copyright 1916, 

by 

FRANK R. KEPLER, Chairman 

First Issue .... October, 1915 

First Edition .... March, 1916 

Second Edition .... July, 1916 

Third Edition, Revised . January, 1921 



0)C!.A614042 



PREFACE 

THE purpose of ''Mechanical Drawing Standards and Con- 
ventions" is to provide students and teachers of mechanical 
drafting with a collection of standard usages based upon the best 
modern drafting-room practice. An attempt to standardize the 
drawing room practice in schools has been made necessary because 
of the varying training of teachers and the obvious desirability 
of having uniform standards and conventions in conformity with 
good commercial work. 

It is imperative that such material should be put within 
easy reach of students and teachers. To supply this need^ as 
evidenced during a number of years of teaching, much of the 
material was brought together into a preliminary issue, which 
was constructively criticised by representatives of nearly fifty 
leading firms of Detroit and vicinity. The suggestions were care- 
fully noted, discussed, and finally decided as the consensus of 
opinion seemed to dictate. School requirements and good educa- 
tional methods have governed the decision of points which did 
not seriously conflict with good industrial practice. The text of 
former issues has been thoroughly revised and many plates 
redrawn and several added. These revisions have been checked 
with present drafting room practice. 

The General Directions and Notes, Directions for Laying 
Out Sheets, general Standards and Conventions come at the 
beginning where they are easily accessible. These are followed 
by the more detailed notes on Conventional Lines Working Draw- 
ings, Dimensions, etc. At the end are found suggestions for Kapid 
Drafting, Inking, Checking Drawings, Tracing. An attempt has 
been made to arrange the plates so that they come opposite the 
page of text which they illustrate. 

Grateful acknowledgment is made of tlie assistance of the 
Committee on Standards and Conventions of the Detroit Manual 
Training Club; of the assistance and encouragement of Mr. P. 
A. Cummins, formerly of Cass Technical High School, now of 
the Educational Department, Solvay Process Company; of Mr. 
I. G. Koehler, co-worker and Head of the Mechanical Drawing 
Department, Cass Technical High School; also for the many 
valuable suggestions of Mr. George E. Willard, with Messrs. 
Wills and Lee, automobile engineers; and of many others. 



8 



A 



PREFACE TO FIRST EDITION 

COMMITTEE on STANDAKDS AND CONVENTIONS 

for Mechanical Drawing was selected by the Executive Com- 



mittee of the Detroit Manual Traininar Club. 



& 



Copies of a preliminary issue of STANDARDS AND CON- 
VENTIONS for Cass Technical High were used as a basis of 
inquiry and criticism. These copies were sent out to fifty rep- 
resentative concerns in Detroit and Michigan. The criticisms 
of a large majority of the representatives of these firms were 
gathered together, carefully noted, and discussed. Points were 
finally decided as the consensus of opinion seemed to indicate. 
School requirements and good educational methods have gov- 
erned the decision of points which did not seriously conflict with 
good industrial practice. 

This first edition is presented with the hope that these 
STANDARDS AND CONVENTIONS, determined as stated 
above, will be generally adopted in the schools. 

The chairman takes this opportunity to acknowledge the 
interest, suggestions and helpfulness of the various members of 
the committee. 

F. R. KEPLER, CHAIRMAN 

CASS TECHNICAL 

L. G. BURGESS, SECY 

NORTHWESTERN 

P. A. CUMMINS 

CASS TECPINICAL 

EDWARD GATES 

CENTRAL 

JOHN F. GRANT 

EASTERN 

D. W. HICKOK 

WESTERN 



PREFACE TO FIRST ISSUE 

THE notes and plates for STANDARDS AND CONVEN- 
TIONS have been brought together by Mr. P. A. Cummins 
and myself for use in Cass Technical High School. They are the 
result of several years' experience in teaching Continuation. 
Evening, and High School classes, and are a study of the require- 
ments of modern drafting room practices. 

Mr. Carnot Iverson, Cass Technical High School, inked in 
all the drawings for the plates and made the original drawings 
for Plates 15 and 16. 

Friendly criticisms of our initial copy will be greatly appre- 
ciated, as it is our endeavor to meet the best drafting-room prac- 
tices. 



STANDARD S/ZE>S OF 3HEETS 

THC MO^r ECONOMiCAL METHOD OF CUTT/NG 
THE YARD ROLL TO OBTAIN THE! STAA/DARD 
SHEETS /S SHOWN /N F/G. / , BY TH/S MULTf- 
RLE SYSTEM J THE LARGE A S/ZE r^AY BE 
SUBO/VfOCD TO GJVE THE SMALLER sS/ZES. 




NOTE. 



SiZES GfVEN ON THE T/GURES ARE THE 
ROUGH CUTTfNG S/ZES. THE L/GHT LINES 
/NDfCATE THE CUTT/NG LINES EOR TR/MMfNG 
THE r/N/SHED DRA\/V/NG. 






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PLATE 1 



GENERAL DIRECTIONS AND NOTES 

The standard sizes of finished drawings shall be 6"x9", 
9"xl2'', 12''xlS'S 18"x24", and 2d:''x86'', with border rectangles 
5i4''x8>i'^ 8"xll", ir'xir% 17''x23'', and 23''x35'' respectively. 
These sizes are chosen for the reason that commercial stock may 
more readily be cut to those dimensions, and the smaller cut 
from the larger without waste, Plate I. 

A very simple and economical method of cutting the paper 
from the yard roll is shown in Plate I, Fig. 1. The extra width 
on the 24''x36" size is for the purpose of leaving thumb tack 
room outside the cutting edge of every drawing when sub-divided. 
A method of cutting a Koyal size (19"x24") sheet, which is quite 
common, is shown in Fig. 2 on the same plate. 

Letters representing the different size drawings shall be as 
follows : 

A for 24"x36" with border 23"x35" 

B '' 18"x24'' " " 17"x23" 

C "■ 12''xl8" " " ir'xir' 

D " 9"xl2'' " '' 8''xll'' 

E " 6"x9" " " 5>4''x8>^" 

Drawings of the first term shall be numbered 101 to 199; 
of the second term, 201 to 299; of the third term, 301 to 399; 
and of the fourth, 401 to 499. The first figure tells at once in 
what school term the drawing is made, and the last figures give 
the consecutive number of the drawing. Thus the drawing rep- 
resenting the thirty-sixth problem in the third term on a 12''xl8" 
sheet would be C-336. 

Drawings to be used in the various shops of the school may 
be numbered consecutively beginning with 1101 preceded by the 
proper letter designating the size of the sheet ; thus : D-1102. A 
record of each drawing shall be kept. 

One drawing from each course may be retained as the prop- 
«rtv of the school. 



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DIRECTIONS 
For Laying Out D-Size Sheets 

{See Plate 2) 

Place a sheet of drawing paper of the size furnished npon 
the drawing board so that the upper edge is in line with the 
upper edge of the tee-square. Put a thumb tack in the upper 
left hand corner, stretch the paper diagonally, and place a sec- 
ond thumb tack in the lower right hand corner. Stretch the 
paper from the center toward the two remaining corners, thus 
securing a flat sheet upon w^hicli to draw. All thumb tacks 
should be so placed as to be outside the cutting lines. Placing 
the tee-square diagonally across the j^aper from corner to corner, 
draw portions of the diagonals near the center, to find the exact 
center of the sheet. 

Placing the scale vertically so that the 41/2'' division lies 
opposite the center, without removing the scale, lay off, 41/2" 
below the center, at the division, and 4", at the I/2' division; 
and also 4i/^" above the center, at the 9^' division, and 4'', at the 
Syo" division. 

In similar manner, place the scale horizontally so that the 
6" division lies opposite the center, lay off 6" and 5%" to the 
left, and 6" and 51/2'' to the right. 

Draw horizontal lines through the points located above and 
those below the center; and vertical lines through the points 
located at the right and those at the left of the center. 

The resulting outer rectangle, 9"xl2'', gives the cutting lines 
on which to trim the finished drawing; the smaller inner rec- 
tangle, 8''xll", is the border rectangle. Observe Plate 2. 

A title block is used in all cases. The title block will appear 
at the bottom of the sheet. The arrangement and ruling will be 
as shown in Plate 4. The title block must be penciled in com- 
plete before the drawing itself is begun. 

Guide lines in pencil only should be drawn for the tops and 
bottoms of all letters. These guide lines are drawn in pencil 
only. 

Each drawing shall first be done in pencil and submitted to 
the instructor for approval or corrections. No part of the draw- 

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ing is to be ''lined in/' inked or traced, until it has been approved 
by the instructor and he has placed his "O. K." on the margin. 

When the drawing is finished, it shall again be submitted 
for final approval before the "O. K." is cut off. It shall then 
be trimmed to the proper size, 9"xl2", and handed in. 



DIRECTIONS 
For Laying Out C-Size Sheets 

{See Plate 3) . 

Place the sheet of drawing paper, provided for the purpose, 
on the drawing board so that one of the long sides is even with 
the upper edge of the T-square, and fasten down. Locate the 
center of the sheet as described for the D-size. Draw two hori- 
zontal lines 12 inches apart and equidistant from the center; 
draw two vertical lines 18 inches apart equidistant from the 
center, thus enclosing a rectangle 12''xl8'', which is the size for 
trimming the finished drawing. Draw a border rectangle 11 "x 
17", leaving 14 " margin on all sides. Observe Plate 3. 

Unless otherwise directed, a title block is to be placed in 
the lower right-hand corner. This title block is to contain the 
name of the school, the title of the drawing, by whom drawn, by 
whom traced, and checked as well as approved, and the number 
of the drawing. It is to be spaced and arranged as shown in 
Plate 4. 

The cutting-lines, border rectangle, title block, and bill of 
material must all be arranged properly in pencil before the 
drawing itself is begun. Be careful to make the drawing accu- 
rate in pencil, making all corrections before inking any part of 
the drawing. Do not begin inking until the penciled drawing 
has been submitted to your instructor for his approval and he 
has placed his "O. K." on the margin. 

AVhen the drawing has been carefully inked or traced it must 
again be submitted to the instructor for his final approval before 
removing it from the drawing board. This approval secured, the 
finished drawing is to be trimmed to the required size, 12"xl8", 
and handed in. 



11 





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12 



STANDARDS AND CONVENTIONS 

The following conventions and standards are to be followed 
in making- all drawings: 

1. The conventional lines of the kinds and weights shown 
are to be used as required. AYhen inked or traced, in either ink 
or pencil, a good contrast must be made between the object and 
other lines. The beginner often makes his object lines too light. 

2. The letters and figures used for notes and dimensions 
shall be after the form adopted — inclined, single, uniform line 
lettering. Plate 6. 

3. All notes on drawings shall be made with capital letters 
3/32" high, made between light penciled guide-lines that dis- 
tance apart. The guide-lines are made in pencil only. 

4. Dimension figures must be made %" high. Fractions are 
to be made twice the height of the whole numbers, with the divi- 
sion line horizontal and in line Avith the dimension line, Plate 6. 



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DIMENSION LINE 



5. Place the dimension figures in the center of the dimension 
line, leaving a convenient space for the figures. Plate 6. 

6. Arrow heads are always to be made narrow, about 1/16" 
wide, 1/8 '' loi^g- They must not be large and spread out. Plate 6. 

7. The Title Block, containing the title of the drawing, is 
placed in the lower right hand corner of the sheet for convenience 
when the drawing is filed. This title block gives the name of 
the school, the name of the draftsman, the initials of the tracer 



13 



DtMENSiON^S FOR B/LL OF MATERIAL 







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REPERENCE NUMBER 






PLATE 5 



14 



and checker, the date of approval, and the drawing number. The 
dimensions for the title block with the position of the items, as 
well as the heights of letters and spaces, are shown in Plate 4. 

8. A Bill of Material is generally placed on all drawings 
for shop purposes and erecting. It may be placed in any con- 
venient space on the drawing, but preferably just above the 
title block and adjacent to the right hand border. The Bill of 
Material must contain the number of parts, the material of 
which they are made, the name of the part, the reference num- 
ber on the drawing, and, if a pattern is required, the pattern 
letter. See paragraph 10. The arrangement of the bill of mate- 
rial must be as shown in Plate 5. The lettering is 3/32" high 
and is done between penciled guide lines which must not be 
inked. The listing of the parts begins at the bottom, a few 
spaces being left at the top for the listing of additional parts 
as occasion demands. Such standard parts as bolts, machine 
screws, washers, etc., are listed but are NOT DRAWN. 

9. Each part shall have a Reference Number, whether the 
part is detailed on the drawing or is a standard part. Each 
number is to appear on or near the piece if detailed ; if standard 
it is to be placed near where it belongs, an arrow showing the 
exact location. Each number is to be 3/16" high and be placed 
within a heavy circle %'' in diameter, the number being of the 
same weight. The number should be made first and then the 
circle drawn, so that the number will appear in the exact center 
of the circle. A corresponding number shall appear in the Bill 
of Material with the name of the part. Plate 5. 

10. Patterns will be listed A, B, etc., in the Bill of Mate- 
rial. The pattern number shall consist of the drawing number 
and the pattern letter. Hence pattern B on Drawing C-556 would 
be Patt. C-556-B. Plate 5. 

CONVENTIONAL LINES 

(>Sfce Plate 6) 

11. Border lines shall be heavy full lines, from 1/32'^ to 
3/16" wide. 

12. Visible edges and outlines of objects shall be repre- 
sented by full, bold lines of medium width. 

15 



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PLATF 6 

16 



13. Hidden edges and outlines of objects shall be repre- 
sented by broken lines, consisting of short %" dashes, consid- 
erably lighter than medium lines, separated by 1/16" spaces. 

11. Dimension lines shall be fine, solid lines, interrupted 
for the figures expressing the dimension and terminated at the 
outer ends by long, narrow arrow-heads; and drawn ^'' or more 
from the outline of the yiew. 

15. Kefereuce, or extension lines, shall be fine, full lines, 
drawn at right angles to the edge measured, from a point 1/32'' 
from the edge and projecting %" beyond the arrow-head. 

16. Center lines shall be fine, broken lines, consisting of 
long %" dashes, separated by single 1/16" dots and 1/16'' spaces. 

17. Projection, or Construction lines, including all lines not 
essential outlines or edges of the object represented, shall be fine 
1/16" dotted lines. These are seldom inked. In penciled draw- 
ings, fine full lines are preferred. 

WORKING DRAWINGS 

18. A working drawing is one made for use in a workshop, 
in building construction, or erecting in the field. 

19. The representation of an object by such a drawing must 
follow the principles of orthographic projection. In all standard 
drawings the third angle is used. Plate 7. 

20. The front yiew must be placed below^ the top-yiew, or 
plan ; the end, or side yiew, at the corresponding side of the front 
yiew, or eleyation; the bottom yiew below the front yiew. Plate 
7. If conditions demand, an end yiew may be placed at the right 
or left of the top-yiew, or plan. 

21. TAyo yiews are generally needed to represent an object. 
Three yiews are often required, while more may be necessary. 
Sometimes one yiew with a section yiew is all that is necessary, 
while in the case of a cylinder one yiew showing the length with 
the diameter stated thus : 3" DIA., will meet all requirements. 
Select the yiews tliat will giye the best idea of the piece, ayoid- 
ing hidden edges. Plate 8, Figs. 1 and 2. 

22. Working drawings are made %", 1", 11/2", 2", 3", 
4", 6", 9" and 12'' to the foot, that being 1/16, 1/12, Vg, 1/6, 
%:? ^? %? % and full size respectiyely. Details are made ful] 

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PLATE 8 
19 



scale or to as large a scale as possible. Scales are not given on 
detail drawings. The 2'' and 4'' scales are to be avoided as 
impractical. 

23. Drawings are made either of the separate parts or of 
the various parts properly assembled. The former are styled 
detail drawings; the latter assembly drawings. 

24. Drawings are made of pieces as they would naturally 
appear in use, in the assembled whole, or in the position required 
for the major tool operations. * 

25. Show all details as near to full size as possible con- 
sistent with size of- sheet. 

ASSEMBLY DRAWINGS 

26. The assembly drawing is designed to show the inter- 
relation of the parts, the space occupied by the machine, the 
name and number of each part, the method of fastening, center 
line distances which can be checked in erecting, and the like. 
The assembly drawing is usually made more elaborate than the 
detail in that shading may be done at times, threads drawn in 
their true form, or gear teeth shown. 

27. The assembly may be sectioned in part to show the inte- 
rior and the working of the component parts. 

28. In engine and machine drawings it is permissible to 
omit in one view some construction which is sufficiently shown 
in anotlier view. This permits the showing of details in the 
mechanism which would otherwise be obscured. 

29. Preliminary assemblies are usually made full size from 
sketches and are used by the designer in working out the action 
of the mechanism. 

30. Partial assemblies are made to show the details of any 
system connected with the macliiue, as the lay-out of winng, and 
piping. 

31. Pij)ing and wiring drawings are often made in isometric 
form in which one picture, or view, may show top, front and all 
details. Such a drawing aids the workman, as it shows at a 
glance the location of all couplings, valves, tees, elbows, and 
other parts. 

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PLATE 9 

21 



DIMENSIONS 

32. Drawings are dimensioned the actual size of the piece, 
regardless of the scale. 

33. Dimensions and notes must be at least 14/' oi' more from 
the drawing. Plate 8, Figs. 3 and 4. 

34. Dimensions are placed so as to read either from the 
right-hand side of the sheet or from the bottom. Plates 8, 9 
and 10. 

35. All notes are placed either horizontally or vertically, 
never at an angle. Plate 8, Fig. 4. 

36. Everything must read from the lower and right-hand 
sides of the sheet. Plates 8, 9 and 10. Figures and notes must 
always read, either from left to right, or from the bottom towards 
the top of the sheet. 

37. Dimension figures, including fractions, are placed at the 
center of the dimension line, unless the space is very limited, 
in which case the arrow-heads and figures are placed on the out- 
side of the space dimensioned. Plate 10. 

38. The common fractions in i/2's, i/4's, %'s, 1/32's, 1/16's, 
1/64's only are used. Where very accurate work is demanded, 
decimals are used. 

39. The division-line of fractions must be in line with the 
dimension line, and never inclined. Plate 10. 

40. On drawings of machinery inches are used up to 48 
inches. 48 inches and above are expressed in feet and inches, 
thus : 4 £L 10 E!^ 4'— 10''. Plate 10. Where all dimensions are 
in inches the inch marks may be omitted. 

41. Inches alone are used on drawings of automobile parts 
and assemblies and in many allied industries. 

42. Over all dimensions should be placed well outside the 
drawing; minor, or detail, dimensions are placed inside these. 
Plates 8 and 9. A series of dimensions should be so arranged 
as to facilitate checking. 

43. Dimensions must not be too far removed from tlie part 
dimensioned. Measurements are placed so as to aid the checker 
and the workmen. Dimensions are often well placed between 
the views. 

22 



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PLATE 10 
23 



44, Keep dimensions off the figure except where there is a 
possibility of confusing the workmen. Plate 8, Fig. 2. 

. 45. Keep related dimensions, i. e., a length and width, on 
the same view if possible. 

46. Dimensions of a detail given in one view must not be 
repeated in another. 

47. Avoid dimensioning from hidden edges. 

48. Never use center lines for dimension lines. 

49. Base dimensions from center lines and finished sur- 
faces. Make the drawing proof against blunders by tying up 
all holes or cuts to center lines or finished surfaces. Plate 8, 
Fig. 4; Plate 9, Fig. 1. 

50. Place center lines through the centers of all circles and 
symmetrical drawings. Show center lines for every hole. Plate 
9 and Plate 11. 

51. Dimension to center lines of circles, not to circumfer- 
ences. Plate 9, Fig. 1. 

52. Circles are dimeilsioned by their diameters; arcs by 
tlieir radii. All radii should be marked K or Kad. and all diam- 
eters Dia. or D, Ream, Turn, Bore, Core, etc. Plate 9, Fig. 1, 
and Plate 10. 

53. Where there are several diameters in a given length it 
is better to give them across the length rather than in an end 
view. Plate 9, Figs. 2 and 3. 

54. Never cross a dimension with a line. Break section 
lines for a dimension or note if j)laced in a sectional area. Plate 
11, Fig. 1. 

55. Since shop drawings are not to be scaled give all neces- 
sary dimensions for laying out and finishing the work. 

56. Drawings are figured for the machinist, cabinet maker, 
or builder, as the case may be. Be careful to give such dimen- 
sions as will be needed by the mechanic in laying out the work, 
making, testing and assembling. All figuring is up to the drafts- 
man. Add all ^^detail" dimensions and give "over all" to aid in 
checking. Leave no adding or subtracting for the workmen. Tliis 
is the draftsman's job. The workman has enough* to figure out 
without doing that of the draftsman. 

24 




SECT/ ON O/V A- A 



F/G. t 



r-TT 

I I I 




FIG. a 



PLATE 11 



25 



NOTES 

57. Do not be afraid to use explanatory notes. Clearness 
is all important. 

58. All left-liand tlireads should be plainly marked. 

59. Handed pieces should be marked Right (or Left) as 
shown. 

60. On tool details it is customary to add a note below 
regarding- material, as Tool Steel, etc., etc., Harden and Grind, 

etc. 

61. On tool details the dimensions of the raw stock from 
which the part is to be made are sometimes given. 

62. Use abbreviations where possible, but be sure the abbre- 
viation is commonly used. The workman reads the drawing, 
not your mind. 

SECTION VIEWS 

63. A section view shows the surface as made by the pass- 
ing of a plane through a piece; a portion of the piece is imag- 
ined cut away to exjDose the hidden parts. The purpose of a 
section is to show the shape of cores, thickness of stock, interior 
mechanism, and assembly. Plate 11. • 

64. The point at which a section is made is indicated by a 
heavy line consisting of short dashes about one-fourth inch long, 
and lettered: as A — A. Fig. 1, Plate 11 shows a section view on 
a broken line. Fig. 1, Plate 12 shows a section through the cen- 
ter of a gear. In the same iigure a revolved section of the arm 
is shown. See Plate 9, Fig. 1, also. 

65. The surface cut by the plane of section is indicated by 
lines at 45 degrees spaced in proportion to the size of the draw- 
ing, usually about 1/16'' apart. Section all details as for cast- 
iron. The various styles of cross-hatching need not be used to 
indicate the material, often that for cast-iron and babbitt only 
being used in actual practice. Examples of some of the more 
common forms of cross-hatching are shown in Plate 18. The 
material is otherwise stated in connection with the name of the 
piece. Cross hatch lines for cast-iron and for babbitt are fine. 
Plate 11 and Plate 20. 

26 




ne. / c^sr ^pur gbar 



^,^M 




Q ^._ j^o T DEPTH or COT 0.£636 ^^ ^^ ^ 
F/G,a. CUT SPUR GEAR 



PLATE 12 

27 



SCREW THREADS 



h^1 ^^"7 



n It^r-'^r 




^HARP V 

P. P^ 



r^i \m 



U.S. STANDARD 
P. 




SQUARE 





BUTTRESS B&S WORM THD. 

CONVEiNTtONAL METHODS 






ta US.STD. THD. 
f^EIR /N. 



fO USSTD.r. 
THD. PER /N. 






^(NGi^E 



DOUBLE US.STD. 




V 




US. sra FORM 



SQUARE 



PLATE 13 

28 



^ DR/UL 



6 



DRILL 



SCRCV>/ THREADS 



wm7A 



r/e i. DRILLED HOLES 



wm ^ 



r/a a A 





^'x/3 TAP 

a s, 3, 



4 TAP /e a^f: 4x/€ tapus.s. 




§X/6 tap 
US.STO.R 




^'xao TAP' 
SHARP V THD L,H, 






r/Ga. TAPPED HOLES 




^"OR/LL c'SfNH 



^ BRIGGS STD. 
PIPE THD. 



FIG, 3 




F/G.^ 



PLATE 14 



29 



66. Never section bolts, nuts, screws, shafts, spindles, keys, 
arms of wheels (lengthwise), gear-teeth, etc. Plate 11, Fig. 2, 
Plate 12, Fig. 1. 

67. Seldom show hidden edges behind the line of section, 
unless clearness positively demands it. It is better to make 
another section view. 

68. Make half section rather than full section views. Plate 
11. 

69. When a section is taken through an assembly, adjoin- 
ing section areas have section lines running in opposite direc- 
tions. Plate 11, Fig. 2. 

THREADS 

70. U. S. Standard, U. S. Standard Form, and V-threads 
should be indicated by alternate light and heavy lines. The 
diameter and pitch should always be given. Plate 13. Either 
method as shown may be used. 

71. Any other than the standard thread should be stated in 
a note. If a screw has a left-hand or multiple thread, a note 
should call attention to the fact. Plate 13, and Plate 14, Fig. 2. 

72. A tapped hole should be shown by a circle indicating 
the size of the drill and a larger concentric circle in hidden edge 
line, indicating the size of the tap. A note should state the 
diameter and number of the tap, thus: l''-8 TAP. U. S. Std. 
Plate 14. 

73. Never make detail drawings of standard screws, bolts 
and nuts. 

FINISH 

74. The finish mark, "/," made crossing the line indicating 
the surface finished, shows that the surface is to be finished as 
left smooth by the tools. Plate 8, Fig. 4; Plate 9, Fig. 1. A 
small fraction placed a little above and to the right of the finish 
mark indicates the amount required for finishing. Plate 11, 
Fig. 1. 

•75. Other special finishes as turn, bore, drill, knurl, ream, 
grind, spot-face, as well as core, are so stated on the drawing. 
Plate 9 and Plate 14. 

30 




31 



MACHINE 6 CREW HEADS, 



HEXAGON 



SQUARE 






FH 



ACROSS FLAT'B 






WHEN O <^ 
WHEN 0>^ 




R 



T=0 

ACROSS 



FLA T^B 



6 






WHEN 0<^ 
" WHEN O >^ 



OVAL r/LLtSTER 



ta^ 




1 



F^IlD 
R=^F 






G*iO 



r/LL.tST£:F( 



"r ^m 



L 




— 0/ 



a=F 



G-£[> 



E^iD 



ROUND FJLLfySTER 



OJ 



3f 



F 



F^/io 



^ 






FLAT.OR 
CO UN TERSUNK 



Ul 



•^D-^ 






G=^D 



^ 



PLATE 16 



32 



ti3 



sSET ^SCREWS. 



%.-. 



1 



r±in 





ROUND 



CUP CONE 

sSET ^CREW ENDS 






FLAT 



rUAT PJVOT ROUND P/VOT HANGER 
/?/ VE TS 



ROUND HEAD 



^STEEPLE HEAD 






m 



C=P/AM or BUTTON 




COUNTERSUNK 



HEAD 
CONJCAL HEAD 



o\E-1 L n 



n 



BHJGGS STANDARD P/PE THREADS 



F-LATTOPANO 
BOTTOM 



ROU^D 

BOTTOM 
rEAT 
TOP 




PEREECT THREADS 
ROUND TOP AND 

BOTTOM 
j4 taper P^flJ^CH^ 



-^ TRREADS-A^aTHPS^ i'f'o7'^^^%^^' J 
TAPER or P/PE END^^ PER PT ;OR j^ PER /N. 



PLATE 17 



33 



L/Mt<rs 






t<60'"CHAMr£R 
— 



/. soc 



.so/ 









na /. 



CENTERS FOR G/R//VO/A/G 






B CEA/TER 



.j£jr. 



^•--t, 



(^ CEA/TER a CE/\/TER 

r/G.a, 




j^OR/LL 6HOLE3 



r,A, O. 




7ZZ2^ 



/ DR/LL 



^3 



¥-1 



I 



Nlftj 



F/O. 3 



PLATE 18 



34 



76. If a piece is to be finished all over, the note, ^'Finish 
all over" may be placed near the drawing of the piece or in con- 
nection with its name in the bill of material. Plate 9, Fig. 2. 

77. On all machine parts use the following note: "•Remove 
all burs." "Break all sharp machined edges." 



LIMITS 



78. In cases where great accuracy is needed the workman is 
required to turn out the piece correct within limits. These vary 
a hundredth to a ten-thousandth, for instance, according to the 
accuracy required. 

79. Limits are expressed decimally. The amount over size 
is placed above the dimension line after the dimension figure 
while the amount under size is placed below the dimension line. 



PATTERN AND FORGING DRAWINGS 



80. There is a growing tendency on the part of manufac- 
turers to send full size pattern drawings showing core prints, 
draft, allowance for finish, parting lines, etc., into the die sink- 
ing or pattern rooms. These drawings are usually inked in on 
the original pencil work to avoid the distortion produced by the 
tracing cloth and blue printing. Pattern and die drawings are 
usually made by experienced pattern or die makers who have 
been trained in drafting. Such drawings are intended to sup- 
plement the ordinary drafts made by each pattern maker or the 
foreman. 

81. Pattern drawings should contain certain notes to assist 
the pattern maker such as "Break all sharp edges except as 
noted." 

82. Forging drawings should be very explicit in regard to 
the shape of the part. All centers should be located and drafts 
shown. Dimensions not related to or required by. the pattern 
or die maker's work need not.be shown. 



35 




36 



CONVCNTtONAL CROS^S SECTfOMNG 




CAer tRON 




CAST sr^SL 




WROUGHT fRON 




BABBfTT 



\mmmmm 





BRAS^ 




COPRER 



. \.^'- 



■©.• 



<^.\o\ 



•c\. 









BRICK CONCRETE 

CONVELNTiONAL BREAKS 



RECTANGULAR BAR 



II 



ROUNO ROO 

zzzzzzm 



c 



v/m/<'<>mA 



PIPE 



PIPE (lENGTH\A//^E) 



PLATE 20 



37 



DECIMAL EQUIVALENTS OF FRACTIONAL 




PARTS OF ONE INCH 




( 015625 


33 


.5i56a5 


64 , 


, 03125 


<54,7 


.53125 


3^2 


046875 


35 32 


.546875 


64 , 


0625 


54 9 


,5625 


5 l<5 


.07ftlF.5 


37 '5 


,578125 


^""l 


.09375 


S+/9 


.59375 


T 3a 


\ 09375 


39^2 


.609375 


64 _L 


.\Z5 


6-4 5 


625 


9 8 


\4.06^5 


4, 5 


.6406E5 


e^s 


. 156Z5 


542/ 


.65625 


II 3Z 


. n\fi75 


4332 


.671875 


64 3 


.1675 


64 ,1 


.6675 


13 16 
64 7 
15 3a 
64 


.203125 
.21875 
.£34375 
J 25 


45 '« 


.703/25 


5423 


.7/8 75 


47 35 


. 734375 


54 3 


_.75 


17 

64 Q 


^ .265625 


4^ 4 


, 765 6Z5 


6^25 


.78125 


I93S 


.2S6A75 


^i^^ 


796875 


64 _s. 


.31 F5 


«-^ /3 


.8125 


21 '6 


.3t8ia5 


53 /5 


.6Z8I25 


64,1 


34.375 


64^7 


.84375 


E3 3Z 


.359375 


5532 


_. 859375 


e4 3_ 


.375 


64 ^ 


,875 


25 8 


,3S06£5 


57 8 


.8906a5 


64,3 


,40625 


642^ 


.90625 


27 32 


>!l?lft7.'5 


^©32 


.921875 


64 7 


4375 


64 15 


.9375 


Z9 16 
64,5 


.453*85 
.46875 


6\ 16 


.953125 


643, 


.96875 


31 M 
64 


.484375 


633^ 


.984375 


64 


1 






vvesLEV Di/xeupv 1 



PLATE 21 



38 



U.S. STANDARD 
THREADS BOLTS AND NUTS 


crt 
u 

h 

UJ 

< 


NO.OFTrfDS 
PER INCH 


DIAMETER 

AT ROOT 

OF THREAD 


DIAMETER 
OF TAP DRILL 


DIMENSIONS OF NUTS 
AND BOLT MEADS 


ACROSS 
FLATS 


ACROSS 
CORNERS 
OF HEX. 


ACROSS 

CORNERS 

OPSQUARE 


THICKNESS 
OF NUT 


r iS 


^4 


20 


0.185 


'V64 


/a 


0.578 


0.707 


!/4 


'/4 


5/,6 


18 


0.240 


/4 


'^32 


0.686 


0.840 


Me 


'%4 


Va 


16 


0.294 


5/6 


'/l<o 


0.794 


0.972 


Vs 


'/32 


^6 


14 


0.345 


^Ve^ 


2%Z 


0.902 


1.105 


7/6 


^%4 


K^ 


13 


0400 


^%4 


V8 


I.OH 


1.237 


yz 


Vie 


9/l<b 


IZ 


0.454 


'5^z 


^>^z 


i.iie 


1.370 


V/6 


^/64 


5/8 


n 


0.507 


•y3z 


l/<b 


1.227 


1.502 


% 


'%Z 


3/4 


(O 


0.620 


4l^4 


ii4 


1.444 


1.765 


5/4 


% 


7/8 





0.73I 


Va 


r/G 


1.660 


2.035 


ys 


^^/^Z 


1 


8 


0.838 


^Vg4 


1^6 


1.877 


2.29S 


1 


'Vie 


l!/8 


7 


0,933 


3/32 


1'-/^^ 


2.093 


2.565 


l!/8 


^%2 


1/4 


7 


1.064 


l^/^E 


z 


2.310 


2.fe2B 


1/4 


1 


If/6 


6 


1.158 


l%z 


2^A 


2.527 


3.093 


P/8 


lV5Z 


l!/z 


6 


1.285 


l%z 


z% 


Z.743 


3.358 


I'/z 


|3/l6 


iVs 


514 


1389 


l^%4 


2^^ 


Z.960 


3.623 


15/6 


l%2 


IV4 


5 


1.490 


1%^ 


2^4 


3.176 


3.889 


IV4 


1% 


iVa 


5 


1.615 


|2/32 


2% 


3393 


4,1S4 


m 


I'y32 


e 


4/z 


I.7II 


1^/64 


3/8^ 


3.609 


4.419 


2 


IV16 


Z'/4 


4'/^ 


\.2>G\ 


2144 


3(4 


4.043 


4.94e 


214 


1^4 


Z'A 


4 


2LM5 


2'%j 


375 


4.476 


5.479 


2/z 


I'Vk. 


2?A 


4 


2.425 


2'j44 


414 


4.909 


6.0IO 


2% 


2'/6 


3 


3/z 


-2.629 


2'Xg 


4V^ 


5.342 


6.540 


3 


2V.4 


3/4 


3/z 


2.879 


2% 


5 


S,775 


7070 


3*/4 


2'A 


3/e 


3!4 


3.IOO 


3^0^ 


5% 


6.20S 


7.600 


3/a 


2';^fe 


3% 


3 


3.317 


sys 


5^4 


6.641 


a 131 


3% 


2ys 


4 


3 


3.567 


3% 


ei/8 


7074 


8.661 


4 


3K6 


4>4 


e% 


3.796 


3^2 


G/e 


7508 


a 191 


4'A 


3J4 


A'/L 


2^/4 


4028 


4%z 


^% 


7.941 


9.72! 


4/z 


3% 


4% 


2-5/8 


4.255 


4^6 


7^ 


6.374 


\0.25Z 


4V4 


3% 


^ 


2/z 


4.480 


4^/6 


7-^ft 


S&07 


I0.782 


a 


3% 


5/4 


Z/£ 


4730 


4% 


3 


9.240 


I L31Z 


5'/4 


4 


5/e 


e% 


4.955 


5J^2 


6% 


9,673 


11,842 


SYz. 


4% 


5V4 


e% 


5.203 


3^2 


5% 


10.106 


12.373 


5^4 


4ya 


e 


214 


5,423 


5/z 


0/8 


10,539 


I2.903 


<b 


4% 



PLATE 22 

39 



APPENDIX 

Rapid Drafting : — By following a few little pointers a drafts- 
man may accomplish more than lie otherwise would. After the 
border line and title are laid out, block out the arrangement first. 
Get the location and general outline first, drawing in the details 
afterwards, thus building up the drawing. It is often well to put 
on the dimensions as the drawing proceeds. While the T-square 
is in hand, draw all the horizontal lines possible ; all vertical and 
oblique lines while the triangles are in use. Proceed in like 
manner with each instrument. In inking, draw all lines of the 
same width with one setting of the pen. Do all the lettering at 
one time. Repeating useless motions hinders. A definite order 
of doing things cannot be too strongly emphasized. 

Precautions to Insure Neatness: — In order to keep the draw- 
ing clean, it will be quite necessary to wipe the dust off the 
triangles and T-square with a clean cloth. Brush or wipe off the 
drawing each time. Brush the particles of rubber away after 
erasing. In the case of a large drawing, the finished portion 
may be kept covered. 

TABLE OF SCALES 



Scale per 




Scale per 


Scale per 




Scale per 


foot 


Size 


inch 


foot 


Size 


inch 


W 


1/48 


1/48" 


2" 


1/6 


1/6^' 


V^" 


1/24 


1/24" 


3" 


1/4 


1/4" 


%" 


1/16 


1/16" 


4" 


1/3 


1/3" 


1" 


1/12 


1/12'' 


6" 


1/2 


1/2" 


11/2" 


1/8 


1/8" 


9" 


3/4 


3/4" 


12" to the foot 


is full 


size. 









iTT'TiTn'iT'TiT'Tn'iriT'TiTiTiTiTiTiTiT'Ti'l'i'ril 



Referring to the 3" scale marked 3 on the architect's scale, 
it is found that the 3" space has been divided into twelve 
equal parts representing inches, every third one of w^hich has 
been marked 3, 6, 9. The divisions representing inches are sul)- 
divided to indicate 1/2", %" and Vg". 



40 



To Use the Scale: — From the zero point/ find the number 
of inches reading to the right, and using the figures 3, 6, and 
9 to aid in the reading. 5" is found, two of the inch divisions 
to the right of the division marked 3, reading from the zero; 
2%" is two and one-half divisions to the right of the zero point. 
1 FT. 7'' is found by reading to left from zero to the longer division 
marked 1 in the groove and to the right from zero to the seven 
inch division. The other scales are similarly divided and sim- 
ilarly used. 

INKING 

Ruling Pen: — The ruling pen has two blades. The distance 
apart of the points or nibs is adjusted by means of a little set 
screw. This adjustment determines the width of the line. The 
right line pen needs especial attention as it is used perhaps more 
than any other instrument. It must be well taken care of and 
thoroughly cleaned. Ink must'not be allowed to dry on the points 
as this will corrode and ruin the pen. 

Having completed the pencil drawing, the student should 
next examine his ruling, or right-line, pen and learn to adjust it 
by means of the little thumb scrigw for the different width of 
lines; fine, medium and heavy. 

Preliminary Practice : — It is well for the student using a rul- 
ing pen for the first time, to draw a number of lines on a loose 
sheet of paper with the triangles as guides, until he is able to 
draw them straight. At first thought this may seem easy ; how- 
ever, the drawing of a straight line requires much practice. 

Manner of Holding and Using the Ruling Pen : — ( 1 ) In draw- 
ing lines Avith a right line pen, see that both blades bear with 
equal force upon the paper. (2) The pen should be inclined 
slightly in the direction of motion. Only pressure enough to 
guide it should be given against the straight edge, otherwise the 
blades will be forced together and a line of unequal width will 
result. (3) The lines are drawn by moving the pen from left 
to right, keeping it parallel to the first position, for if it is moved 
away from or toward the body while tracing a line, the point 
of the pen will become closer or farther away from the guiding 
edge and the line will be wavy. (4) To lessen the danger of 
blotting, the guiding edge should be slightly removed from the 
line to be drawn so that the pen point in tracing the line will 
not come in contact with it. 

Manner of Using the Compass: — (1) As with the ruling pen, 
the blades of the compass must bear evenly upon the paper. To at- 
tain this, the compass legs will have to be adjusted in the joints 

41 



so that they will be perpendicular to the paper. (2) In describ- 
ing arcs, allow only the weight of the compass to bear npon the 
needle point, as greater pressure will ca:use the point to wear a 
hole in the paper. A slight pressure may be given to the pen 
.point, however. (3) The top of the compass should be but 
slightly inclined in the direction of the motion. 

Hints for Inking in a Drawing: — (1) Draw all lines of the 
same width with one setting of the pen to insure uniform width 
of line throughout the drawing. (2) When several lines radiate 
from a point, the lines should be drawn from the point, not to- 
ward it, allowing each line to dry before drawing the next one 
in order to j) re vent a blot which is very likely to be made at the 
point. (3) Since it is easier to make a straight line meet a 
curve than otherwise, do the compass work first, then the straight 
lines. (4) In erasing ink lines, the best draftsmen use the steel 
eraser first. Afterward a good, clean rubber. A clean, hard, 
smooth substance is then iised to make the paper smooth again 
and thus prevent the ink from spreading. Use a clean cloth or 
brush to remove the particles of rubber. (5) The student should 
always strive to be neat and should keep covered that portion of 
the drawing which he is not working upon at the time. 

AN ORDER OF INKING 

Group I. Medium lines — Visible object lines. 

1. Circles and arcs of circles. 

2. Irregular curves. 

3. Horizontal lines; begin with lines at top of sheet. 

4. Vertical lines; begin with lines at left of sheet. 

5. Oblique lines. 

Group II. Lines somewhat lighter than medium — Hidden edges. 

Follow same order as Group I. 
Group III. Fine hair lines — Center, reference and dimension 
lines. 

Follow same order as Group I. 
Group IV. Pen work — Dimensions and arrow-heads. Notes. 

Title. 
Group V. Section lines. 
Group VI. Heavy lines — Border lines. 

42 



TRACING 

It is often desirable to make a more permanent and service- 
able record of a drawing than would be possible if only the inked 
original drawing were used. To accomplish this a tracing of the 
penciled drawing is made on tracing cloth. From this tracing as 
many blue-prints as desirable may be made — these are durable, 
since they will w^ithstand the wear and the danger of erasure from 
the weather and hard usage. 

The tracing cloth should be cut somewhat larger than the 
drawing, so that the thumb-tack holes may be removed when the 
tracing is trimmed to the proper size. This can readily be done, 
since 36'' cloth actually measures 37'' wide, being 36" wide be- 
tween the red lines near the edge. 

Tack the cloth down to the board so that it will be tight 
and free from wrinkles, as the tracing may be done more rapidly. 
The cloth should have no creases or breaks in it from ill usage. 
Either the dull or the glossy side of the cloth may be used. A 
great many prefer and use the dull side because in the drafting 
room corrections in pencil may more readily be made on this 
side than on the glossy side. 

Dust the surface over with chalk, magnesia or talcum powder. 
Kub this lightly into the surface and brush all the loose particles 
off thoroughly to rid the surface of grease and grit and to insure 
a ready flow of the ink. 

In order to maintain a uniform width of line throughout 
keep the same amount of ink in the pen, about a quarter of an 
inch at the most. Keep the pen clean. It will be necessary to 
clean the pen often, as little particles of chalk will be picked up 
which interfere with the even flow of the ink. If it is impossible 
to complete the whole tracing at one sitting finish one part, in- 
cluding circles, straight lines, medium and fine. This is most 
desirable, as the cloth is liable to stretch during the intervening 
time between sittings, making it difficult to readjust the trac- 
ing to the drawing. 

Erasing: — Use an ordinary eraser in erasing. Never use one 
with sand in it. A steel eraser should be used only with great 
care. These either destroy the surface of the cloth, making it 
impossible to retrace, or a hole is cut in the cloth, ruining the 
whole tracing. After erasing it is often necessary to build up 
from a fine line to one of full weight. 

43 



CHECKING DRAWINGS 



In checking see that : 

1. The most illustrative views are selected and correctly pro- 
jected. 

2. All conventional lines are made according to adopted stand- 
ards and graded to show contrast. 

3. Center lines for all circles and large arcs are drawn. 

4. That necessary dimensions are given, requiring no calcu- 
lations by the workman. 

5. Eelated dimensions appear on the same view, if possible. 

6. Minor and over-all dimensions check not only with the scale, 
but also by addition. 

7. Dimensions and notes are not repeated. 

8. Arrow-heads, figures and lettering are made uniform and 
neat. 

9. All finished surfaces are"" marked. 

10. All sections and notes which will add to the clearness of 
the drawing are properly made. 

11. Where accuracy demands, all dimensions are "tied up" to 
center lines or finished surfaces. 

12. The assembly checks for clearance of moving parts, and also 
that the various parts function properly. 

13. All holes for accurate fits are made standard; and parts 
fitting thus are made under or over size as the case demands. 

14. The bill of material is complete as to - quantity, material, 
contents, and reference numbers. 

15. Standard stock parts are called for in the bill of material. 

16. Limits are given on all decimal fractions. 



44 



